Conventionally, a large number of plain bearings (bushes) have been used for automatic transmissions. However, in order to prevent seizure caused in the bushes or to reduce torque required for the automatic transmissions, the plain bearings have been substituted by drawn cup needle roller bearings.
As the drawn cup needle roller bearing, it is known to use a drawn cup needle roller bearing, the thickness of which is reduced so that the height of the cross section of the bearing can be 1.5 to 2.5 mm, or a drawn cup needle roller bearing having a seal ring so that a quantity of lubricant passing through the needle bearing can be the same as that of the bush (For example, refer to Patent Documents 1 to 3).
Specifically, a drawn cup needle roller bearing 100 shown in FIG. 21 includes: a shell (an outer ring having a flange) 101; a cage 102; and a plurality of needles 103, wherein the height of the cross section of the bearing is approximately 1.5 mm and shaft diameter is 17 to 33 mm. A drawn cup needle roller bearing 110 shown in FIG. 22 includes: a shell 111; a cage 112; and a plurality of needles 113. The drawn cup needle roller bearing 110 further includes a seal ring 114, the height of the cross section of which is approximately 2 mm, for controlling a quantity of lubricant passing through the needle bearing, wherein the height of the cross section of the bearing is 3 to 3.5 mm and the shaft diameter is 13 to 43 mm.
The seal ring 114 of the drawn cup needle roller bearing 110 shown in FIG. 22 is made by cutting working. After completing the cutting working, heat treatment is executed for preventing abrasion caused by a contact with an opponent member.
Patent Document 1: Japanese Patent Unexamined Publication JP-A-6-294418
Patent Document 2: Japanese Patent Unexamined Publication JP-A-2000-291669
Patent Document 3: Japanese Utility Model Unexamined Publication JP-UM-B-6-23776